PanelView: Use geometry() instead of geometryByDistance() for computing mask
GeometryByDistance() returns the place where the panel should be at a given moment; however it might not have moved there yet, thus it's better to use the actual screen geometry. If there's a mismatch between the two, e.g. when moving the panel around, then the mapFromGlobal() function would place the mask outside the screen area.
BUG: 478923 FIXED-IN: 6.0
(cherry picked from commit 1e6a908f)